Seeing Spots At 10nm

By Ed Sperling
The relentless march to smaller process nodes means the defects are getting smaller, more numerous, and much harder to find.

That explains why Applied Materials and KLA-Tencor both introduced new defect review and classification tools last week. The move to the 1x nm is on the top of both companies’ agendas, and with that comes defects on the walls of finFETs in addition to planar defects, not to mention increased density and more of everything.

“What’s new is multidimensional imaging,” said Ehud Tzuri, who does strategic marketing for Applied Materials’ process diagnostics and control. “We’ve added 360 degree topography, so you can look at a defect from different directions, and from each direction get information.”

Included are tilt capabilities—which is significant considering the inspection equipment is the size of a small trailer—to examine the sidewall of finFETs or features. “We’ve also introduced back-scattering electron detection, which is important for finFETs,” Tzuri said.

One other important feature involves abstraction of the defect data and classifying it as critical or non-critical. This is one of the key advancements in equipment from Applied and KLA. These machines typically are scanning thousands of defects an hour, with new cycles being run every day. The result is that defects have to be understood, then classified to determine whether there is a problem with a particular process—or the latest iteration of that process.

KLA, meanwhile, rolled out is own defect detection and review technology update, also targeted at the 1x nm process. Keith Wells, vice president and general manager of the company’s WIN division, compared the new challenge to finding a penny in the state of California—even if it’s obscured by foliage or falls into a crack in the floor.

The challenge, he said, is maintaining the same gigapixel/second processing rate, which KLA has been running at since 2005. “With multiple patterning, 3D NAND and back-end of line critical design rules there are a huge number of OPC rules at the back end of line,” Wells said. “The industry has been caught off guard with OPC, and even though it’s done a fantastic job there are a lot of escapes. The result is that people thought errors were corrected and they didn’t print that way.”

He said the key is to identify defects vs. nuisances, and that requires lowering the background noise—the fuzziness or grain in images—to improve resolution—while also adding performance improvements to keep pace with the complexity and density of new devices.